Ive noticed the "min_required_rpm" line in the Engines.cfg is inactive. Currently the default is 400rpm and cannot be changed.
Additinaly it would be great if we could set the max starter RPM for piston engines. This already exists for turbines. "starter_N1_max_pct" Just a simple "Starter_max_rpm".
Typical starter rpms are around 150-250 rpm for smaller engines. https://youtu.be/LQ_b1w2ba-o?t=28